Electric switch.



Wins/E5555 H. E. CLIFFORD.

ELECTRIC SWITCH.

APPLICATION FILED MAY 29. I913.

Patented May 8, 1917.

TI i ll F R f 13 :ff: 2

a b ,/7 2; m 9 a v I INYENTUH Hana .EI CLIFIF'UHD m I UNITED STATES PATENT OFFICE HARRY E. CLIFFORD, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC swiroii.

Application filed May 29, 1913.

To all whom it may concern:

Be it known that I, HARRY E. CLIFFORD, a citizen of the United States, residing at Cambridge, county of Middlesex, State .of 1

Massachusetts, have invented certain new and useful Improvements in Electric Switches, of which the following is a specification.

My invention relates to electric switches and more particularly to switches in which the circuit is broken in oil or a similar arc extinguishing medium which may under certain conditions form explosive mixtures with air.

In oil switches, the oil vessel of the switch is usually only partially filled with oil, thus leaving an air space above the oil. The contacts separate however and the arc is formed beneath the surface of the oil. Oftentimes inflammable gases rich in hydrocarbons are evolved from the oil and mix with the air in the upper portion of the oil vessel of the switch until an exceedingly explosive mixture of air and inflammable gases is formed. Opening the switchwhen the air space contains such an explosive mixture, may cause the ignition of the mixture thereby producing a destructive explosion.

The object of my invention is to prevent explosions due to the formation of explosive or inflammable mixtures ofgase s in devices of the oil switch type. To this end, T prevent the formation of explosive mixtures of air and gases in the air space of the vessel containing oil or some similar arc extinguishing liquid capable of producing explosive mixtures with air. I preferably accomplish this result by introducing into the vessel a suitable medium, such as an inert gas or vapor, which will not form an explosive mixture in the presence of the are extinguishing liquid. I prefer to so arrange the parts that the inert gaswill not only prevent the formation of an explosive mixture but will also wash out of the air space of the switch all gaseous products evolved from the arc extinguishing liquid.

The novel features which I believeto be characteristic of my invention will be defined The features of construction and mode of operation will be understood by reference to the following description taken in connection with the accompanying drawing in which, merely for purposes of illustration, Ihave shown in elevation and partly in section one form in Specification of Letters Patent.

Patented May 8, 191?.

Serial No. 770,637.

which my invention may be embodied in an oil switch of the ordinary type of construction.

The figure shows a switch in which the oil is contained in a suitable vessel 1, the level of the oil being represented by the dotted line a b. The oil vessel is made air-tight by a top portion 2 through which passes insulators 3 and 4, projecting beneath the surface of the oil and containing leads 5 and 6 which are connected to fixed contacts 7 and 8 on the lower end of the insulators 3 and 4 and beneath the surface of the oil. A bridglng contact 9 cooperates with the fixed contacts and is operated in the customary mannorby suitable switch mechanism 10.

The space above the oil is kept filled with some suitable inert medium or gas, which prevents the formation of an explosive mixture. This inert medium or gas is supplied to the oil vessel 1 in any suitable way, as, for example, by a reservoir or generator 11 in communication with the oil vessel and containing material from which an inert gas or vapor may be generated. This reservoir or generator 11 is provided with some suitable heater, such as an electrical heating unit 12, placed near the bottom of the generator and operated to heat the material contained in it. The inert medium or gas forms an inert atmosphere in the switch, and preferably circulates through the space above the oil, leaving the generator and passing through an outlet tube 13 into the oil vessel 1 and re- 'turning to the generator by the return or inlet tube 14.

The level of the liquid in the generator is preferably, as shown by the dotted line 0 d, above the level of the inlet tube 14 in order to assist the circulation of the inert gas through the system. The inert gas may be thoroughly dried by any suitable dehydrating agent placed in the system at any suitreservoir or generator 11 may contain a suitable inert medium, as carbon dioxid, or may be filled to a level just above that of. the inlet tube 14 with material from which an inert gas may be generated. This material may be any liquid or solid which will generate an inert gas or vapor, such as carbon tetrachlorid, chloroform, trichlorethylene, etc. lVhen a liquid is used special care is taken to see that it is free from moisture, as even a very small amount of moisture will greatly impair the insulating properties of the oil. I prefer to use dehydrated carbon tetrachlorid, which has a comparatively low boiling point and exists as a very inert vapor when heated. Carbon tetrachlorid is a very good insulator, both in liquid form and when vaporized, and if mixed with oil does not impair the insulating properties of the latter. If some of the carbon tetrachlorid vapor should condense in the air chamber of the oil-containing vessel and mix with the oil, no injury will result. A further advantage in using carbon tetrachlorid is its solvent action for mineral oil with which it is miscible in all proportions. The carbon tetrachlorid vapor carries the oil vapors from the oil vessel by entrainment and in condensing dissolves the oil vapors and washes them into the generator where said vapors are held in'solution.

When carbon tetrachlorid is usedit is placed in the generator 11 to the level shown and is heated by means of the heating unit 12. The carbon tetrachlorid is slowly vaporized and the inert vapor passes from the generator through the outlet tube 13, over the superheating unit 15 and into the air chamber of the oil vessel 1. As carbon tetrachlorid vapor is heavier than air, it displaces the air and fills the chamber with carbon tetrachlorid, vapor, which is not inflammable or explosive. The carbon tetrachlorid vapor and air pass from the oilcontaining vessel 1 through the return or inlet tube 14 back to the generator, the carbon tetrachlorid vapor carrying by entrainment any oil vapor which is evolved in the oilcontaining. vessel. In passing through the return or inlet tube 14, the oil and carbon tetrachlorid vapors are partially condensed,

and return to the generator 11 in a liquidstate. In condensing, the carbon tetrachlorid dissolves a greater portion of the oil vapor before it reaches the generator. All uncondensed oil vapor upon reaching the generator however, is readily dissolved by the liquid carbon tetrachlorid therein, and is held in solution permanently, as the temperature of vaporization of the carbon tetrachlorid is far below that of the oil.

The circulation of carbon tetrachlorid vapor through the oil switching device washes out all oil vapors as fast as the vapors evolve and dissolves and collects them in the generator 11. As a result the oil switch is kept filled with the inert carbon tetrachlorid vapor and all oil vapors evolved are constantly removed. Even when a disruptive arc occurs of such potential that it rises above the surface of the oil, there is no explosion as there is no explosive gaseous mixture to be ignited. On the contrary, the carbon tetrachlorid vapor acts to quench the arc.

My invention may be embodied in many other forms than that shown and described and I, therefore, do not desire to be restricted to the precise construction shown, but intend to cover by the appended claims all changes and modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is,

1. The method of maintaining an inert atmosphere in an electrical device containing oil, which consists in vaporizing a fluid miscible with the oil, passing the vapor through the space in said device above the oil, removing all gaseous products in said space, condensing the mixture of gases and vapor, returning the condensed mixture to said fluid, and holding the condensed gases in solution with said fluid.

2. The method of preventing the formation of explosive gaseous mixtures in a circuit interrupting device containing oil, which consists in vaporizing carbon tetrachlorid, passing the vapor through the space in said device above the oil, removing thereby all gaseous products in said space as fast as such are formed, cooling said mixture of gases and vapors removed from said device, allowing the return of said vapors to said device and preventing the return of said gases. I

3. The method of preventing the formation of explosive gaseous mixtures in an oil switch, which consists in vaporizing a fluid which does not impair the dielectric properties of the oil, passing said vapor through they switch to cleanse said switch of all gaseous products as fast as such are formed, condensing the mixture of gases and vapor, returning the mixture to the fluid, revaporizing the condensed fluid, and trapping the condensed gases in the fluid reservoir.

4. The method of preventing the formation of explosive gaseous mixtures in a circuit interrupting device containing oil,

which consists 1n vaporizing a fluid capable of dissolving the oil, circulating said vapor over the oil in said device, carrying off by entrainment from said device the gaseous products of volatilization formed from the oil, and condensing said gaseous products in said fluid.

5. The method of preventing the formation of explosive gaseous mixtures in a circuit-interrupting device containing oil,

ass ease which consists in vaporizing carbon tetrafrom said device the gaseous products of volatilization formed from the disrupted oil, and condensing said gaseous products in said carbon tetrachlorid.

6, A circuit interrupting device comprising a vessel containing oil, relatively movable coiiperating contacts separable beneath the oil in said vessel, a generator of inert vapor, means for passing said vapor through the space above the oil in said vessel, to remove all gaseous products therein, and means for condensing said mixture of vapor and gaseous products'and returning said mixture to said generator Where said gaseous products "are retained and prevented from returning to said oil vessel.

7. A circuit interrupting device compris ing a vessel containing oil, relatively moV able cooperating contacts separable beneath the oil in said vessel, a generator of carbon tetrachlorid vapor, means for conducting said vapor from said generator through the space above the oil in said vessel to remove all gaseous products and maintain an atmosphere of carbon tetrachlorid vapor therein,

and means for conducting the mixture of vapor and gaseous products from said vessel to said generator Where said vapor and gases are separated and said gases trapped in said generator.

8. A circuit-interrupting device, comprising an oil vessel, a vapor generating vessel arranged to generate an inert vapor, means for circulating said inert vapor over the oil in said-vessel to carry off the gaseous products as fast as such rise to the oil surface, and means for condensing said vapors as they leave the said oil vessel.

9. A circuit-interrupting device, comprising an oil vessel, a vapor-generating vessel, an inlet tube and an outlet tube connecting said generating vessel to said oil vessel, means for superheating the vapor in its passage into said oil vessel, and means for condensing the gases before they return to said generating vessel.

In Witness whereof, I have hereunto set my hand this twenty-seventh day of May,

HARRY E. CLIFFORD. Witnesses:

' DAVID HEALD,

WINNIFRED H001). 

